Technical Abstract:
This study was conducted to evaluate ultrafiltration-diafiltration (UF-DF) as a means to improve the extractability of wet-milled corn germ protein and determine its effects on the functional properties of the recovered protein product. Wet germ and finished (dried) germ proteins were extracted by using 0.1M NaCl at 50°C. Major steps in the method were homogenization, stirring, centrifugation, UF-DF and freeze-drying. UF-DF increased protein extraction efficiency of wet germ while that of dried germ remained similar to what we observed for the baseline method (saline extraction without UF-DF). The recovered freeze-dried UF-DF protein from both germ samples showed the same unusual solubility profile; i.e., the amount of soluble protein was essentially unchanged under acidic, neutral, and alkaline conditions. However, UF-DF finished germ protein was markedly more soluble (80% soluble protein vs. 50% soluble protein in wet germ at pH 2-10). UF-DF protein extracts from both germ samples also had emulsifying capacities and water-holding capacities that were notably greater than those of germ protein recovered by the baseline method, but this favorable effect by UF-DF was not observed for emulsion stability and foaming properties.